Electronic printers, often referred to as serial printers, print one or some portion of a character at a time as the printer moves along the length of the line, say, from left to right across the paper.
Electronic scales previously available utilize an electronic printer having a rotating drum with a helix or other mechanism for rapidly driving the electronic print head back and forth to produce successive lines of print. The electronic printer may be energized when moving in only one or both directions. The paper is advanced one line after each line is printed to space the lines an appropriate distance from one another.
Serial printers may be capable of printing an entire character at a time but more often print by composing a character through the selective actuation of a multiplicity of wires to form the characters from dots as the wires are selectively actuated while the print head traverses the paper with each character being formed by the deposition of dots of ink. The mechanism employed for repeatedly moving the print head from side to side to traverse the paper is complicated, expensive, and subject to wear. It also requires precision mechanical parts which occasionally get out of adjustment and need repair. Such traversing mechanisms also make the equipment bulky and increase the cost of the equipment significantly.
Printers of the general type described are not well suited for printing on a variety of different kinds of paper or other recording medium in sheet form. The present invention is particularly well suited for use as a printer for a weigh scale. In many applications utilizing such scales, great versatility is needed with respect to the sheet material upon which information is printed. Sheets may comprise small or large slips of paper, invoices, bills of lading that can be either card stock or paper. It may also comprise 81/4.times.11" sheets or other larger size sheets of paper as well as documents or tickets of various sizes or sealed envelopes. Consequently, prior printers are limited as to the size, format, and thickness of the paper or other recording medium to be printed under the control of electronic data received from a scale or other source and supplied to the printer as electronic data signals that are fed through a data processor or other remote print signal source.
Other printers store paper in rolls and feed the roll stock from the storage roll to the print head but these devices can only be used to print on paper from the roll. In other equipment, complicated controls are needed for the carriage and for determining margins mechanically.
U.S. Pat. No. 4,021,608 is an example of an electronic data printer of the type using a continuous tape supplied from a roll stock. In accordance with the patent, tape is supplied from a roll tape dispenser and passed across a thermal print head where information is printed on the tape. On the tape can be printed only one line of type. The apparatus responses a paper drive mechanism and in addition is not suitable for printing cut sheets in a variety of sizes since only tape from the supply roll can be used.
U.S. Pat. No. 3,767,020 describes an automatic printer which is manually positionable for printing on articles of virtually any size. The printer is held in the hand and is moved manually across the article to be printed. While suitable for certain applications, the device is not satisfactory in applications with which the present invention is concerned. The primary objection is that the hand-held printer is unfamiliar and one must be trained to use it. It may also be awkward to use and likely to produce printed lines at various angles on the sheet. Consequently, the resulting printed copy may not have the desired appearance. Moreover, it is not suited for printing several lines parallel to one another or for printing lines which are parallel to the bottom edge of the sheet and centered on the sheet, that is to say, with equal margins on each side.
In view of the shortcomings of the prior art it is the general objective of the invention to overcome these problems and to provide a printer of simple construction with a manual paper feed and a stationary print head suited for printing on any type of recording medium. The recording medium may consist of units such as cut sheets of any size, tickets, documents, booklets, folders or even envelopes of various sizes. It is also an object to provide a device that without either a paper drive or a print head drive mechanism will print a line of type oriented along a predetermined axis with respect to the sides and edges of the sheet and yet requires no special operator training so that unskilled operators such as truck drivers, dock hands, warehouse workers, and others who are having articles weighed will find that the manner of using the printer to be immediately obvious.
These and other more detailed and specific objects will be apparent from the following description of the invention in which the invention will be described in more detail by way of example.